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A level Statistics doubt??Post your doubts here!

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it should be like this ((19-b-19)/1.5<z<(19.5+b)/1.5)>pphieinverse of (0.8)???
i think sub answer from 1?
 
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from table 0.842 for 0.8 probability

then 2(b/0.15)-1 = 0.842
2(b/0.15)=1.842
(b/0.15)=0.921
its actually phi-inverse of 0.9 not 0.8
this is how i did it6.png
the shaded area is 0.8 so u'll have
2phi(z) - 1 = 0.8
phi(z) = 0.9
so z= phi-inverse 0.9
=1.281 its +/- 1.281
then u can use these values to get b which will also be +/- so that u can find 1.9-b and 1.9+b
hope u got it :)
 
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its actually phi-inverse of 0.9 not 0.8
this is how i did itView attachment 26737
the shaded area is 0.8 so u'll have
2phi(z) - 1 = 0.8
phi(z) = 0.9
so z= phi-inverse 0.9
=1.281 its +/- 1.281
then u can use these values to get b which will also be +/- so that u can find 1.9-b and 1.9+b
hope u got it :)

ah thanks.. I guess I have started showing signs of stats getting way over my head =,= .. And I should try and study something other than stats :D Hope I don't do these mistakes in the CIE paper!
 
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ah thanks.. I guess I have started showing signs of stats getting way over my head =,= .. And I should try and study something other than stats :D Hope I don't do these mistakes in the CIE paper!
ur welcome:)
dnt worry it happens...stats is just a problem.....
 
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if u see Y can only take the values 0 2 or 4 and since 0 would be when its either 2,2 4,4 or 6,6 u multiply the indiviual probabilities of getting a 2 4 and 6 and add them eg 0.5x0.5 +0.4x0.4+0.1x0.1=0.42
likewise u can solve for 2 and 4 i hope u get what i said :)
 
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if u see Y can only take the values 0 2 or 4 and since 0 would be when its either 2,2 4,4 or 6,6 u multiply the indiviual probabilities of getting a 2 4 and 6 and add them eg 0.5x0.5 +0.4x0.4+0.1x0.1=0.42
likewise u can solve for 2 and 4 i hope u get what i said :)
ok thanx :D
 
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salam...am struckd on one part ov the question...
In a random sample of 1000 body feathers from birds of a certain species, how many would the researcher expect to find with lenghts more than 1 standard deviation from the mean??
 
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salam...am struckd on one part ov the question...
In a random sample of 1000 body feathers from birds of a certain species, how many would the researcher expect to find with lenghts more than 1 standard deviation from the mean??
2/3
 
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salam...am struckd on one part ov the question...
In a random sample of 1000 body feathers from birds of a certain species, how many would the researcher expect to find with lenghts more than 1 standard deviation from the mean??

3alaikumissalam.

Work out the P(X > mean + sd)

I can't remember which year that is, but I will just give you a quick example.

If the question is X~N(10,5^2) (10 mean and 5 sd) and you are looking for lengths MORE THAN 1 sd from the mean, that means you need to work out P(X > 10 +5)

That is P(X>15).

Whatever answer you get, multiply it by 1000.

Hope that helps. :)
 
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